Linear motor for use in machine tool
The invention is a linear motor that improves the processing speed of machine tools is also a linear motor with significantly reduced cogging force, with which high-speed and high-accuracy processing can be realized. More specifically, the invention is a linear motor for use in a machine tool comprising a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction; the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to the rows of the permanent magnets on the both faces of the stator; and magnetic cores that are disposed on both ends of the movers such that the distance between the magnetic cores and the rows of the permanent magnets is longer than that between the armature cores and the rows of the permanent magnets. Moreover, provided is a laser processing machine in which the above-mentioned permanent magnet type linear motor is used for a three-dimensional moving mechanism.
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The present invention relates to a permanent magnet type linear motor that is used broadly for the purpose of, for example, driving a moving part of a machine tool.
DESCRIPTION OF THE RELATED ART
Since a machine tool needs a large thrust, a linear motor comprising a stator in which a plurality of permanent magnets are mounted on a plate-like yoke at even intervals such that the polarities of the permanent magnets alternate in a direction in which a mover moves; and the mover that is constituted by armature cores and armature coils and that is opposed to the row of the magnets of the stator is used.
Conventional linear motors associated with the present invention will be described with reference to FIGS. 11 to 16.
In the linear motor 130 shown in
When the linear motor shown in
In order to solve this problem, Japanese Patent Application Unexamined Publication No. 10-257750/1998 discloses a linear motor 150 in which, as shown in
Thus, a linear motor 170 disclosed in Japanese Patent Application Unexamined Publication No. 2002-34231 and shown in
With the conventional linear motor 170 that is thus designed, a high thrust can be obtained, but an attraction force works between the permanent magnets and the magnetic cores in the moving direction even when the current is not passing through the coils. This is referred to as “cogging”. If the cogging is large, then position control of the linear motor is not performed appropriately, and thus there has been a problem in that the processing accuracy of the laser processing machine deteriorates.
SUMMARY OF THE INVENTIONIt is an object of the present invention to provide a linear motor with which the processing accuracy of machine tools is improved, and also to provide a linear motor with significantly reduced cogging force, with which high-speed and high-accuracy processing can be realized.
A first aspect of the present invention provides a linear motor for use in a machine tool comprising: a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction; the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to the rows of the permanent magnets on the both faces of the stator; and magnetic cores that are disposed on both ends of the movers and that are disposed such that the distance between the magnetic cores and the rows of the permanent magnets is longer than the distance between the armature cores and the rows of the permanent magnets.
The magnetic cores may be referred to as “auxiliary cores”, and the armature cores may be referred to as “main cores”.
A second aspect of the present invention provides a linear motor for use in a machine tool comprising: a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction; and the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to the rows of the permanent magnets on the both faces of the stator, wherein each of the movers comprises two mover blocks, each bock having a length that is eight times longer than a magnet pitch τ, which is the sum of the width of each of the permanent magnets and the gap distance between adjacent permanent magnets, and having nine armature cores wound with the armature coils in U, V, and W phases of three each, and wherein the length of a spacing between the two blocks is set to be ½ of the magnet pitch τ.
A third aspect of the present invention provides a linear motor for use in a machine tool comprising: a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction; and the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to the rows of the permanent magnets on the both faces of the stator, wherein each of the movers comprises three mover blocks, each block having a length that is eight times longer than a magnet pitch τ, which is the sum of the length of each of the permanent magnets and the gap distance between adjacent permanent magnets, and having nine armature cores wound with the armature coils in U, V, and W phases of three each, and wherein the length of a spacing between adjacent blocks is set to be ⅓ of the magnet pitch τ.
A fourth aspect of the present invention provides a linear motor for use in a machine tool comprising: a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction; and the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to the rows of the permanent magnets on the both faces of the stator, wherein each of the movers comprises three mover blocks, each block having a length that is eight times longer than a magnet pitch τ, which is the sum of the length of each of the permanent magnets and the gap distance between adjacent permanent magnets, and having nine armature cores wound with the armature coils in U, V, and W phases of three each, and wherein the length of a spacing between adjacent blocks is set to be ⅔ of the magnet pitch τ.
Moreover, the present invention provides laser processing machines in which these permanent magnet type linear motors are used for a three-dimensional moving mechanism. The present invention provides a machine tool comprising the linear motor. Examples of the machine tool may include MC (machining center) and an electric discharge machine.
According to the first aspect of the present invention, by disposing the magnetic cores (auxiliary cores) on both ends of the movers and by making the length of the magnetic cores shorter than that of the armature cores (main cores), the cogging force can be significantly reduced, and thus high-accuracy processing becomes possible. According to the second aspect of the present invention, by disposing the two mover blocks, each block having a length that is eight times longer than the stator magnet pitch and having nine teeth (armature cores) wound with the armature coils in the respective phases of three each, and by setting the spacing between the blocks to be ½ of the stator magnet pitch, the cogging force can be significantly reduced, and thus high-accuracy processing becomes possible.
According to the third aspect of the present invention, by disposing the three mover blocks, each block having a length that is eight times longer than the stator magnet pitch and having nine teeth (armature cores) wound with the armature coils in the respective phases of three each, and by setting the spacing between adjacent blocks to be ⅓ of the stator magnet pitch, the cogging force can be significantly reduced, and thus high-accuracy processing becomes possible.
According to the fourth aspect of the present invention, by disposing the three mover blocks, each block having a length that is eight times longer than the stator magnet pitch and having nine teeth (armature cores) wound with the armature coils in the respective phases of three each, the cogging force can be significantly reduced, and thus high-accuracy processing becomes possible.
BRIEF DESCRIPTION OF THE DRAWINGS
Examples of the permanent magnets that are used in the present invention include, but not particularly limited to, Nd- and Sm-based magnets. The orientation of the magnets is perpendicular to the plate-like yoke.
There is no particular limitation regarding the magnetic cores (auxiliary cores) and the armature cores (main cores) that are used in the present invention, as long as the cores are magnetic, but it is preferable that the auxiliary cores and the main cores are formed into one piece. That is to say, although the auxiliary cores may be made of the same material as the main cores or a different material from that of the main cores, it is preferable that the auxiliary cores are made of the same material as the main cores and can be obtained integrally with the main cores. However, the auxiliary cores are not wound with coils. Specific examples of the material of the auxiliary cores include magnetic materials such as silicon steel, low carbon steel, and magnetic stainless steel.
According to the present invention, the auxiliary cores that are disposed on both ends of the rows of the movers are shorter than the inner main cores, and the difference in length between the auxiliary cores and the inner main cores is preferably 5 mm or more and more preferably 6 to 15 mm. The length of the magnetic cores is as described above, and the cross-sectional shape of the magnetic cores is preferably, but not particularly limited to, rectangular or trapezoid.
Referring to
As shown in
Therefore, if the magnetic flux distribution at both ends of the armature cores is adjusted appropriately, then the cogging force can be reduced. That is, according to the present invention, by providing the auxiliary cores and by adjusting the magnetic flux distribution by changing the difference ΔH between a face of the auxiliary cores and that of the main cores, the cogging force can be reduced.
An embodiment according to the second aspect of the present invention will be described with reference to
Each mover block has a length that is eight times longer than the stator magnet pitch, and nine teeth (armature cores) of the mover. The two mover blocks are serially disposed in the traveling direction, and preferably a spacer 27 having a size that is ½ of the stator magnet pitch is inserted between the two blocks (between the armature coils). However, it is also possible that there is a space having a length that is ½ of the magnet pitch between the two blocks.
The material of the spacer 27 is preferably a non-magnetic material, such as non-magnetic stainless steel or aluminum, so as to eliminate magnetic interference between the two mover blocks. There is no particular limitation regarding the shape of the spacer, but the shape of a rectangular parallelepiped block is preferable.
Examples of the method for connecting the spacer to each mover block include a method of fixing the spacer with an adhesive and a method of providing another frame and mechanically fixing the spacer in conjunction with the mover to that frame. Regarding the winding method of the armature coils 25, it is sufficient that the coils in the U, V, and W phases are disposed such that the total number of coils of each phase is three, and the arrangement of the U, V, and W phases can be chosen as appropriate. For example, if, in the first block, U, V, and W phase coils of three each are concentratedly wound around teeth in this order from the left tooth in the drawing, then, in the second block, a V phase coil is wound around the first tooth, W and U phase coils of three each are wound around teeth in this order from the second tooth, and two V phase coils are wound around the last two teeth.
Referring to
In
An embodiment according to the third aspect of the present invention will be described with reference to
Each mover block has a length that is eight times longer than the stator magnet pitch, and nine teeth (armature cores) of the mover. The three mover blocks are serially disposed in the traveling direction, and preferably a spacer 37 having a size that is ⅓ of the stator magnet pitch is inserted between adjacent blocks (between the armature coils). However, it is also possible that there is a space having a length that is ⅓ of the magnet pitch between adjacent blocks.
The material of the spacer 37 is preferably a non-magnetic material, such as non-magnetic stainless steel or aluminum, so as to eliminate magnetic interference between the three mover blocks. There is no particular limitation regarding the shape of the spacer, but the shape of a rectangular parallelepiped block is preferable. Examples of the method for connecting the spacer to each mover block include a method of fixing the spacer with an adhesive and a method of providing another frame and mechanically fixing the spacer in conjunction with the mover to that frame.
Regarding the winding method of the armature coils 35, it is sufficient that the coils in the U, V, and W phases are disposed such that the total number of coils of each phase is three, and the arrangement of the U, V, and W phases can be chosen as appropriate. For example, if, in the first block, U, V, and W phase coils of three each are concentratedly wound around teeth in this order from the left tooth in the drawing, then W, U, and V phase coils of three each are wound around teeth in the second block in this order from the left tooth, and V, W, and U phase coils of three each are wound around teeth in the third block in this order from the left tooth.
Referring to
In
An embodiment according to the fourth aspect of the present invention will be described with reference to
Each mover block has a length that is eight times longer than the stator magnet pitch, and nine teeth (armature cores) of the mover. The three mover blocks are serially disposed in the traveling direction, and preferably a spacer 47 having a size that is ⅔ of the stator magnet pitch is inserted between adjacent blocks (between the armature coils). However, it is also possible that there is a space having a length that is ⅔ of the magnet pitch between adjacent blocks.
The material of the spacer 47 is preferably a non-magnetic material, such as non-magnetic stainless steel or aluminum, so as to eliminate magnetic interference between the three mover blocks. There is no particular limitation regarding the shape of the spacer, but the shape of a rectangular parallelepiped block is preferable. Examples of the method for connecting the spacer to each mover block include a method of fixing the spacer with an adhesive and a method of providing another frame and mechanically fixing the spacer in conjunction with the mover to that frame.
Regarding the winding method of the armature coils 45, it is sufficient that the coils in the U, V, and W phases are disposed such that the total number of coils of each phase is three, and the arrangement of the U, V, and W phases can be chosen as appropriate. For example, if, in the first block, U, V, and W phase coils of three each are concentratedly wound around teeth in this order from the left tooth in the drawing, then V, W, and U phase coils of three each are wound around teeth in the second block in this order from the left tooth, and W, U, and V phase coils of three each are wound around teeth in the third block in this order from the left tooth.
Referring to
In
According to the present invention including the first to fourth aspects, the linear motor in which the auxiliary cores are provided as described above can be applied to a laser processing machine in which the linear motor is used for a three-dimensional moving mechanism in X-, Y-, and Z-axis directions. With the laser processing machine of the present invention, unevenness in the thrust is eliminated due to a reduction in the cogging force, and position control accuracy is increased, and thus high-speed and high-accuracy processing can be performed.
Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.
EXAMPLE 1 Auxiliary cores were provided as shown in
The linear motor provided with the auxiliary cores as described above could be applied to a laser processing machine in which the linear motor was used for a three-dimensional moving mechanism in X-, Y-, and Z-axis directions.
EXAMPLE 2 As shown in
As shown by a solid line in
The linear motor provided above could be applied to a laser processing machine in which the linear motor was used for a three-dimensional moving mechanism in X-, Y-, and Z-axis directions.
EXAMPLE 3 As shown in
As shown by a solid line in
Thus, by disposing the three blocks of the mover cores with a spacing that is ⅓ of the magnet pitch between adjacent blocks, the cogging force could be reduced.
The linear motor provided above could be applied to a laser processing machine in which the linear motor was used for a three-dimensional transfer mechanism in X-, Y-, and Z-axis directions.
EXAMPLE 4 As shown in
As shown by a solid line in
The linear motor provided above could be applied to a laser processing machine in which the linear motor was used for a three-dimensional moving mechanism in X-, Y-, and Z-axis directions.
Claims
1. A linear motor for use in a machine tool comprising:
- a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction;
- the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to rows of the permanent magnets on the both faces of the stator, and
- magnetic cores that are disposed on both ends of the movers such that the distance between the magnetic cores and the rows of the permanent magnets is longer than that between the armature cores and the rows of the permanent magnets.
2. The linear motor for use in a machine tool according to claim 1, wherein the distance between the magnetic cores and the rows of the permanent magnets is longer than the distance between the armature cores and the rows of the permanent magnets by 5 mm or more.
3. A linear motor for use in a machine tool comprising:
- a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of movers move and alternating in the moving direction; and
- the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to rows of the permanent magnets on the both faces of the stator,
- wherein each of the movers comprises two mover blocks, each block having a length that is eight times longer than a magnet pitch τ, which is the sum of the width of each of the permanent magnets and the gas distance between adjacent permanent magnets, and having nine armature cores wound with the armature coils in U, V, and W phases of three each, and
- wherein the length of a spacing between the two blocks is set to be ½ of the magnet pitch τ.
4. The linear motor for use in a machine tool according to claim 3, further comprising a non-magnetic spacer between said two blocks in order to set said length of the spacing between the two blocks to be ½ of the magnet pitch τ.
5. A linear motor for use in a machine tool comprising:
- a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of mover moves and alternating in the moving direction; and
- the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to rows of the permanent magnets on the both faces of the stator,
- wherein each of the movers comprises three mover blocks, each block having a length that is eight times longer than a magnet pitch τ, which is the sum of the length of each of the permanent magnets and the gap distance between adjacent permanent magnets, and having nine armature cores wound with the armature coils in U, V, and W phases of three each, and
- wherein the length of a spacing between adjacent blocks is set to be ⅓ of the magnet pitch τ.
6. The linear motor for use in a machine tool according to claim 5, further comprising a non-magnetic spacer between adjacent blocks in order to set the length of the spacing between adjacent blocks to be ⅓ of the magnet pitch τ.
7. A linear motor for use in a machine tool comprising:
- a stator in which a plurality of permanent magnets having the same shape are mounted on both faces of a plate-like yoke at even intervals such that the permanent magnets have polarities being perpendicular to a direction in which a pair of mover moves and alternating in the moving direction; and
- the movers in which armature cores wound with armature coils are disposed such that the armature cores are opposed to rows of the permanent magnets on the both faces of the stator,
- wherein each of the movers comprises three mover blocks, each block having a length that is eight times longer than a magnet pitch τ, which is the sum of the length of each of the permanent magnets and the gap distance between adjacent permanent magnets, and having nine armature cores wound with the armature coils in U, V, and W phases of three each, and
- wherein the length of a spacing between adjacent blocks is set to be ⅔ of the magnet pitch τ.
8. The linear motor for use in a machine tool according to claim 7, wherein the linear motor comprises a non-magnetic spacer between adjacent blocks in order to set the length of the spacing between adjacent blocks to be ⅔ of the magnet pitch τ.
9. A laser processing machine in which the linear motor for use in a machine tool according to claim 1 is used for a three-dimensional moving mechanism.
10. A laser processing machine in which the linear motor for use in a machine tool according to claim 3 is used for a three-dimensional moving mechanism.
11. A laser processing machine in which the linear motor for use in a machine tool according to claim 5 is used for a three-dimensional moving mechanism.
12. A laser processing machine in which the linear motor for use in a machine tool according to claim 7 is used for a three-dimensional moving mechanism.
13. A machine tool comprising the linear motor according to claim 1.
14. A machine tool comprising the linear motor according to claim 3.
15. A machine tool comprising the linear motor according to claim 5.
16. A machine tool comprising the linear motor according to claim 7.
Type: Application
Filed: Jul 18, 2005
Publication Date: Jan 19, 2006
Applicant:
Inventors: Koji Miyata (Takefu-shi), Masanobu Uchida (Takefu-shi), Ken Ohashi (Takefu-shi)
Application Number: 11/184,645
International Classification: H02K 41/00 (20060101);